There are many units to define Linear Density (counts, thickness) of polyester & nylon threads and yarns. Common textile calculation formulas are divided into two categories: fixed-length system formulas and fixed-weight system formulas:

‌Fixed-Length System Formulas:‌

(1) Denier (D)=g/L×9000

(2) Tex=g/L×1000

(3) Dtex=g/L×10000

Where g is the weight of the thread (grams) and L is the length of the thread (meters).

‌Fixed-Weight System Formulas:‌

(1) Metric Count (N): N=L/G

Where G is the weight of the thread (grams) and L is the length of the thread (meters).

(2) English Count (S): S=L/(G×840)

Where G is the weight of the thread (pounds) and L is the length of the thread (yards).

‌Conversion Formulas:‌ ^[1]

(1) Metric Count (N) to Denier (D): D=9000/N

(2) English Count (S) to Denier (D): D=5315/S

(3) Decitex (dtex) to Tex (tex): 1 tex=10 dtex

(4) Tex (tex) to Denier (D): 1 tex=D/9

(5) Tex (tex) to English Count (S): tex=K/S.

‌K-values:‌ Pure cotton yarn: K=583.1 Pure chemical fiber: K=590.5 Polyester-cotton yarn: K=587.6K Cotton-viscose yarn (75:25): K=584.8 Vinyl-cotton yarn (50:50): K=587.0

(6) Tex (tex) to Metric Count (N): tex=1000/N

(7) Decitex (dtex) to Denier (D): 1 D=0.9 dtex

(8) Decitex (dtex) to English Count (S): dtex=10K/S

‌K-values:‌ Pure cotton yarn: K=583.1 Pure chemical fiber: K=590.5 Polyester-cotton yarn: K=587.6K Cotton-viscose yarn (75:25): K=584.8 Vinyl-cotton yarn (50:50): K=587.0

(9) Decitex (dtex) to Metric Count (N): dtex=10000/N

[1] China Cotton Textile Association
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